Thermostatic device.



UNITED STATES PATENT OFFICE. K

GEORGE A. JAMES, OF SAN FRANCISCO, CALIFORNIA.

THEBMOS'IATIC DEVICE.

Specification of Letters Patent.

Application filed February 16, 1914, Serial No. 819,079. Renewed June it, 1817. Serial No. 175,214.

Devices, of which the following is a specifi-.

cation.

The object of the resent invention is to provide a thermostatic device which may be included in an electric circuit closed by the action of heat or cold u on the device, and which will not be close by a shock or ar tending to cause vibration of the device.

In the accompanying drawing, Figure 1 is a front elevation of my improved thermostatic device; Fig. 2 is a vertical section on the line 22 of Fig. 1, an electric circuit bein omitted; Fig. 3 is a vertical section on the me 3-3 of Fig. 2; Fig. 4 is a cross section on the line 4-4 of Fig. 1.

Referring to the drawing, 1 indicates a suitable insulating box or casing having closed sides, back and top, and an open front. The bottom 2 of the casing extends only through the rear half of the depth of the casing, and thelower ends of the sides are enlarged or thickened inwardly to form suports 3, to which are bolted by bolts 4, the ower ends of the brass strips 6 of two pairs of thermostatic members 7, 7', 8, 8'. To these strips are riveted, as shown at 9, vulcanite strips 11. By reason of the different expansion by heat of the brass and vulcanite strips, said thermostatic members bend with each change of temperature. The portions of the strips which are riveted together are of the same length and thickness for the front and back thermostatic members, and consequently the bendin efi'ect onthem is the same when subjects to the same temerature. The rear thermostatic members, however, are Protected from a change in temperature 0 the surrounding atmosphere or objects by means of a partition 12 slidable in grooves 13 in the innerfaces of the enlargements 3 in the sides of the box, and close to the front faces of the bottom 2, said partition extending to substantially the same height as the connected. arts of the respective strips. This partition forms with the sides, back and bottom of the box a chamber open only at the top and containing the rear thermostatic members 7', 8', so that the air around said rear members can circulate very slowly and the temperature of said rear members is not changed, with a chan e in temperature of objects, or of the atmosp ere, in proximity to the box, so quickly as the front thermostatic members, which are exposed to the heat radiated from said objects or to convection of heat by the atmosphere. Said device therefore maybe utilized to indicate a rapid change of temperature of surrounding objects or of the atmosphere, for the front thermostatic members respond immediately to said rapid chan e, whereas the rear thermostatic members 0 not respond so rapidly thereto. To enable this indication to be made there extend rearwardly from the upper portions of the brass strips of the front thermostatic members arms 14 having on their outer sides cut-away portions 16 across the ends of each of which extends a horizontal platinum wire 17, adapted to contact with a vertical platinum wire 18 extending across the ends of a cut-away portion 19 in the upper end of the brass strip of the corresponding rear thermostatic memher. -The rear thermostatic members are connected electrically by means of a bent spring plate 20, interposed between, and in contact with, the bolts which attach the lower ends of the brass strips of said mem- I hers to the box, and the bolts which attach to the box the lower portions of the brass strips of the front members are connected to an electric circuit 21 through a battery 22 and electro-magnet 23.

The four thermostatic members having equal deviations with a given change of temperature, and the rear thermostatic mem bers being better protected than the front members from sudden changes of temperature, it results that, when a sufiicient sudden change of temperature occurs, the front members both bend until the platinum wires 17 carried thereby make contact with the platinum wires 18 carried by the rear members, and the circuit is closed. After a length of time dependin upon the extent to which the rear mem ers are protected from changes in temperature, that is, upon the height to which the partition extends between the front and rear members, the rear members will become of the same temperature as the front members, and the cir- In order that a thermostatic device of brought into contact by a shock or jar which will'cause the members to vibrate, thus closing the circuit and causing a false alarm, H

.or other result which is not caused by'a change in temperature. It is for this-reason that I employ two pairs of thermostatic members instead of one, and I also secure upon the brass strips of the members of one pair Weights 26 of brass or other heavy metal, since the.period of vibration of a vibratable object varies With its mass, and by securing heavy weights to one pair I cause their vibration period to difier considerably from that of the other pair. Since the vibration-periods of the two pairs differ, the members of said pair are never simultaneously in contact with each other, and consequently there is no closure of the elecor other results due to' the vibrations caused by a jar, and am therefore able to render th instrument more sensitive.-

I by no means, however, limit my invention to the precise means here employed for rendering unequal the vibration periods of the two pairs of members.

I claim p An apparatus comprising an electric circuit, pairs of vibratable thermostatic members in series therein, the members of each pair being adapted to contact with each other when vibrated, the vibration period of a member of one pair being difierent from that of a member of the other pair;

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.v

GEORGE A; JAMES.

Witnesses I M. WRIGHT, D. B. RICHARD. 

